Epoxy resin photoresist with iodoform and bismuth triphenyl

ABSTRACT

Photopolymerizable compositions and processes for photopolymerizing such compositions are provided, said process comprising admixing with said epoxides, photosensitive organohalogen compounds in combination with an organometallic compound and thereafter applying energy to the resulting mixture. The organohalogens decompose to liberate an active catalyst which then serves to initiate polymerization of the epoxide material. The organometallic compound functions synergistically with the organohalogen to enhance the film forming properties of the resulting polymer and or sensitivity of the polymerizable system.

This is a division of application Ser. No. 369,086, filed June 11, 1973,now U.S. Pat. No. 3,895,954.

BACKGROUND OF THE INVENTION

It had heretofore been known in isolated instances in the literaturethat epoxy monomers may be polymerized by the action of electromagneticradiation. For example, Penezek et al. in Die Makromolekular Chemie, 97(1966) have reported that gamma radiation will effect polymerization ofcyclohexene oxide. However, this type of reaction does not generallyoccur with most epoxy monomers. Additionally gamma radiation is not aconvenient source of radiation and not as useful as the ultraviolet andvisible regions of the spectrum. Therefore, for quite some time now,polymerization of epoxy monomers has been carried out by heating to hightemperatures the monomer in which a chemical compound was incorporated,until catalysts contained therein were activated. The activation of thecatalyst upon heating thereby initiated polymerization of the epoxymonomers. These methods, though successful, are unsatisfactory in thatcareful attention must be given to staying within the temperaturelimitations of the system involved. In order to prevent the harmfuleffects of heat curing, it is often necessary to extend the curing cyclean unreasonable length of time.

More recently, it has been discovered that epoxides may bephotopolymerized employing aryl diazonium salts as photo-sensitiveprecursors. Such a procedure forms the subject matter of U.S. Pat. No.3,708,296 issued Jan. 2, 1973 to Sheldon I. Schlesinger.

It has recently been discovered that another class of compounds, theorganohalogens, are effectively photosensitive to initiatephotopolymerization of epoxides and such compounds offer a viable andattractive alternative to the use of aryl diazonium catalysts. Suchdiscovery is disclosed and claimed in copending U.S. application Ser.No. 369,007 filed June 11, 1973, now abandoned, and commonly assignedherewith by S. Schlesinger entitled "Organohalogen Compounds AsPhotoinitiators of Epoxy Photopolymerization".

Organohalogens have been known for some time as free-radical initiatorsin photopolymerization processes where polymerization is initiated viathe double bonds of an unsaturated compound. Free-radicalpolymerizations however are known to suffer in general from theundesirable characteristic that the polymerization is subject toinhibition by molecular oxygen. Also free radical inhibitors such as4-methoxyphenol are often added to prevent premature polymerizations ofcoating mixtures stored in the dark.

It has now been discovered that the photopolymerization of epoxidematerials employing organohalogen compounds as photoinitiators isenhanced synergistically when such polymerization is effected in thepresence of an organometallic compound containing a Group V metal asdescribed herein. Moreover, it has been discovered that suchorganometallic compounds when combined with organohalogens functionsynergistically to enhance the film forming properties of the polymerformed and/or enhances the sensitivity of the polymerizable system.

The above discovery of the effectiveness of organohalogen-organometallicsystems in the polymerization of cationically polymerizable epoxides issurprising in view of the known tendency of organohalogens to formfree-radicals on exposure to radiation and the difficulties normallyexperienced with free-radical initiated polymerization taken togetherwith the fact that epoxides are known to be polymerizable through acationic mechanism. Indeed, workers in the art have reported thatorganohalogen compounds are ineffective for such cationicpolymerizations. See for example, Cripps et al., U.S. Pat. No. 3,347,676issued Oct. 17, 1967, wherein polychlorinated biphenyls were ineffectiveto initiate photopolymerization of cationically initiated monomers.Another example is Smith, U.S. Pat. No. 3,515,552 issued June 2, 1970,which discloses that a specific class of compounds, e.g., vinyl etherscharacterized by undergoing more rapid polymerization than othercationically polymerizable materials, were photopolymerized withorganohalogen initiators. In this procedure, however, polymerizationtakes place via the double bonds in the vinyl ethers. To date, there hasbeen no procedure which recognized that epoxide compounds, polymerizablecationically through the opening of oxirane rings rather than throughdouble bonds, could be effectively photopolymerized employingorganohalogen compounds in combination with organometallic compounds.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to photopolymerizablecompositions comprising an epoxide material polymerizable to highermolecular weights and, as a latent catalyst precursor therefor, anorganohalogen compound which decomposes upon application of energy torelease an active catalyst which effects the polymerization incombination with an organometallic compound which enhances thefilm-forming properties of the polymer and the sensitivity of thepolymerizable system and to processes for effecting such polymerization.

DETAILED DESCRIPTION OF THE INVENTION

Thus, in accordance with the procedure of this invention, a mixture isformed of an epoxide material in admixture with an organohalogencompound as a latent catalyst precursor and an organometallic compoundin which the metal is a member of Group V of the Periodic Chart as anenhancer therefor. The composition at a convenient time subsequently isexposed to electromagnetic radiation or other energy sources to releasean active catalyst or catalysts which effects the polymerization of theepoxide material.

The Organohalogens

Any organic halogen compound that decomposes under the action ofsuitable energy sources for example, electromagnetic radiation, torelease an active catalyst effective to initiate polymerization of theepoxide material, and in which the halogen is of an atomic number of 9 -53, e.g., fluorine, chlorine, bromine, and iodine, may be employedherein.

The organohalogen is believed to decompose under the action of suchenergy to liberate halogen atoms as shown in equation 1, utilizingcarbon tetrabromide, for example: ##STR1## The halogen is then believedto initiate polymerization of the epoxide by either or several of: A.Abstracting a hydrogen atom from a solvent or the monomer to form anacid (HX) or

B. reacting with a metal, for example, a metal substrate to which thecomposition is applied, to form a Lewis acid halide or

C. acting as a Lewis acid by itself to initiate polymerization.

Preferably, the compound will exhibit bond dissociation energies for thecarbon to halogen bond of between about 40 and 70 kilogram calories permole or less and especially 60 kilogram calories per mole or less. Ingeneral, organic bromides and iodides require less energy to dissociate,provide stronger acids upon dissociation, and are preferred herein forthese reasons. Similarly, aliphatic halides require less energy for bonddissociation than aromatic halides, while polyhalogenated compoundsprovide more available halides per mole of compound than monohalides.Accordingly, the most preferred compounds for use herein will bepolyhalogenated aliphatic bromides or iodides or polyhalogenatedaliphatic chains as substituents on aromatic rings.

Although the above discussed compounds are preferred, many and variousorganohalogens may be employed in which the organic radicals are alkyl,aryl, aralkyl, alkaryl, alkoxy, aroxy, heterocyclic, organo-metallic,etc., as long as they are compatible with the epoxide component of thesystem and function to release an active catalyst in accordance with theinvention.

The following illustrative organohalogen compounds may be employed ascomponents of the photopolymerizable compositions herein: carbontetrabromide; tetra (bromomethyl) methane; tetrabromoethylene,1,2,3,4-tetrabromobutane; trichloroethoxyethanol; p-iodobenzene;bromobenzene; iodoform; p-bromophenol; p-iodobiphenyl;N-bromosuccinimide; α,α'-dibromo-p-xylene; phenylquinaldinium iodide;phenylchromium iodide-chloroform complex, (C₆ H₅) Cr.sup.. I.sup..2CHCl₃ ; chloroform; bromoform; 2,6-dibromophenol; 1-bromo-2-naphthol;p-bromoaniline; hexachloro-p-xylene; trichloroacetanilide;p-bromodimethylaniline; tetrachlorotetrahydronaphthalene;α,α,α',α'-tetrabromoxylene; hexabromoethane; hexabromocyclohexane;tetrafluoroethylene; hexafluoroethane; etc.

The Epoxide

Any monomeric or prepolymeric material, or mixture of such materials, ofsuitable viscosity or suitable miscibility in solvents, which ispolymerizable to higher molecular weights through the action of acationic catalyst, may be utilized in the process and compositions ofthe present invention. In a preferred embodiment, any polymerizable,monomeric or prepolymeric epoxide material or mixture of such epoxidematerials, of suitable viscosity alone or when dissolved in a suitablesolvent, may be utilized. The classic epoxy resin is obtained by thewell known reaction of epichlorohydrin and bisphenol A(4,4'-isopropylidenediphenol). The reaction product is believed to havethe form of a polyglycidyl ether of bisphenol A (the glycidyl groupbeing more formally referred to as the 2,3-epoxypropyl group) and thismay be thought of as a polyether derived from the diphenol and glycidol(2,3-epoxy-1-propanol). The structure usually assigned to the resinousproduct is ##SPC1##

a viscous liquid epoxy resin, average molecular weight about 380, isobtained by reacting the epichlorohydrin in high molecular proportionrelative to the bisphenol A, the reaction product containing well over85 mole per cent of the monomeric diglycidyl ether of bisphenol A (n=0),which may be named 2,2-bis[p-(2,3-epoxypropoxy)phenyl]propane, andsmaller proportions of polymers in which n is an integer equal to 1, 2,3, etc. This product exemplifies epoxide monomers and prepolymers,having a moderate molecular weight, preferably of the order of 1,000, orless, which may be cross-linked or otherwise polymerized in accordancewith the invention, whereby cleavage of the terminal epoxy or oxiranerings is initiated by the action of the active catalyst released whenenergy is applied to the latent polymerization catalyst.

Many other epoxide materials are available in polymerizable monomeric orprepolymeric forms. Among these are 1,2-epoxycyclohexane (cyclohexeneoxide, also named 7-oxabicyclo-[4.1.0]heptane); and vinylcyclohexenedioxide, more specifically named3-(epoxyethyl)-7-oxabicyclo[4.1.0]-heptane or1,2-epoxy-4-(epoxyethyl)cyclohexane. Ethylene oxide

(oxirane, ##STR2## the simplest epoxy ring) and its homologuesgenerally, e.g., propylene oxide (1,2-epoxypropane) and 2,3-epoxybutane,are themselves useful; other useful epoxidic cyclic ethers are the C₃ Oring compound trimethylene oxide (oxetane), derivatives thereof such as3,3-bis(chloromethyl)oxetane (also named2,2-bis(chloromethyl)-1,3-epoxypropane), and the C₄ O ring compoundtetrahydrofuran, as examples. Other epoxidized cycloalkenes may be used,a readily available polycyclic diepoxide being dicyclopentadienedioxide, more specifically identified as3,4-8,9-diepoxytricyclo[5.2.1.0².6 ]decane. A suitable polyfunctionalcyclic ether is 1,3,5-trioxane.

Glycidyl esters of acrylic acid and of its homologs, methacrylic acidand crotonic acid, are vinyl epoxy monomers of particular interest.Other such monomers are allyl glycidyl ether(1-allyloxy-2,3-epoxypropane) and copolymers thereof with glycidylmethacrylate particularly as disclosed and claimed in co-pending U.S.Application, Ser. No. 297,829 filed Oct. 16, 1972, as well as glycidylphenyl ether (1,2-epoxy-3-phenoxypropane). Another readily availableproduct is a mixture of ethers of the structure ##STR3## where R isalkyl, that is, glycidyl alkyl ethers. One such mixture containspredominantly glycidy octyl ether and decyl glycidyl ether; anothercontains dodecyl glycidyl ether and glycidyl tetradecyl ether.Epoxidized novolak and epoxy cresol novolak prepolymers likewise may beused, as well as polyolefin (e.g. polyethylene) epoxides. The latter areexemplified by epoxidized, low molecular weight by-products of thepolymerization of ethylene, which may be separated as mixtures high in1-alkenes in the range from about 10 to 20 carbon atoms, that is fromabout 1-decene to about 1-eicosene. Epoxidation then provides mixturesof the corresponding 1,2-epoxyalkanes, examples being mixtures high inthe 1,2-epoxy derivatives of alkanes having 11 to 14 carbons, or having15 to 18 carbons.

Esters of epoxidized cyclic alcohols, or of epoxidizedcycloalkanecarboxylic acids, or of both, provide useful epoxide orpolyepoxide materials. Thus a suitable ester of epoxidizedcyclohexanemethanol and epoxidized cyclohexanecarboxylic acid is thediepoxide (3,4-epoxycyclohexyl)methyl 3,4-epoxycyclohexanecarboxylate.Another suitable diepoxide may be obtained as an ester of a substituted(epoxycycloalkyl)methanol and a dibasic acid, for example,bis[3,4,-epoxy-6-methylcyclohexyl)methyl] adipate, which may be namedalternatively bis[4-methyl-7-oxabicyclo-[4.1.0]hept-3-yl)methyl]adipate. Diepoxide monomeric materials may be obtained conveniently asbis(epoxyalkyl) ethers of glycols, an example being the diglycidyl etherof 1,4-butanediol, that is, 1,4-bis-(2,3-epoxypropoxy)butane. Thisdiepoxide is related to the diglycidyl ether of bisphenol A, shown aboveas 2,2-bis[p-2,3-epoxypropoxy)phenyl]propane.

The Organometallic Compound

The organometallic compounds suitable for use herein may be representedby the formula:

    R.sub.3 M

wherein M is a metal selected from Group V of the Periodic Chart of theElements including P, As, Sb and Bi; R is an organic radical, preferablyhydrocarbyl such as alkyl, aryl, alkaryl, aralkyl, cycloalkyl,alkcycloalkyl, etc. or hydrogen with the proviso that at least one R isan organic radical.

Exemplary of compounds represented by the formula are organophosphinessuch as tricyclohexylphosphines, trioctyl phosphine, diphenyl cyclohexylphosphine, tributyl phosphine, trihexenyl phosphine, trixylyl phosphine,triethyl phosphine, dicyclohexyl phosphine, cyclohexyl phosphine,trihexyl phosphine and triphenyl phosphine; organobismuthines such astrixylyl bismuthine, triphenyl bismuthine, tributyl bismuthine,tricyclohexyl bismuthine, tridecyl bismuthine, diphenyl octyl bismuthineethyl ditolyl bismuthine, etc.; organoarsines such as tricyclohexylarsine, triphenyl arsine, trioctyl arsine, diphenyl butyl arsine,trixylylarsine, tridecyl arsine, dicyclohexyl arsine, tricyclohexylarsine, etc. organostibines such as triphenyl stibene, tridodecylstibene, tributyl stibene, dicyclohexylstibine, tri(2-ethylhexyl)stibine, etc.

Especially preferred for use herein are such compounds containing tri(aryl) groups with triphenyl bismuthine being the most preferredcompound.

The exact mechanism by which the organometallic compounds function toenhance the sensitivity and film forming properties in the polymerizablesystem is not known. It is possible that the photolysis product of theorganohalogen compound combines with the organometallic compound in someway to function as it does. However, the beneficial results of thepresent invention are useful without regard to the theoreticalexplanation for the phenomena. As illustrated further hereinbelow, theorganometallic compound does not function to initiatephotopolymerization of the polymerizable material in the absence of anorganohalogen. Yet, when combined therewith, such compounds exert adecided synergistic effect.

A general application of the process of the invention can be as follows:the photopolymerizable composition as heretofore defined is admixed in asuitable medium and, for instance, in one embodiment of the invention,the mixture is thereafter coated on a suitable substrate such as metalplate, plastic or paper, and the substrate is exposed to an energysource. On exposure, the catalyst precursor or precursors decompose torelease an active catalyst which initiates the polymerization of theepoxy monomer. The resulting polymer is resistant to most solvents andchemicals.

The source of radiation for carrying out the method of the presentinvention can be any suitable source, such as the ultraviolet actinicradiation produced from a mercury, xenon, or carbon arc, or the electronbeam produced in a suitably evacuated cathode ray gun. The onlylimitation placed on the radiation source used is that it must have anenergy level at the irradiated film sufficient to impart to thepolymerizable system energy at an intensity high enough to reach thedecomposition level of the photosensitive compounds. As previouslynoted, the wavelength (frequency) range of actinic radiation is chosento obtain sufficient absorption of energy to excite the desireddecomposition.

For an imaging system, the mixture, which may contain a suitable solventin substantial proportions, is coated on a metal plate, dried ifnecessary to remove solvent present, and the plate is exposed toultraviolet light through a mask or negative. The light initiatespolymerization which propagates rapidly in the exposed image areas. Theresulting polymer in the exposed areas is resistant to many or mostsolvents and chemicals, while the unexposed areas can be washed withsuitable solvents to leave a reversal image of the polymer in thisembodiment.

The polymers produced by the polymerizing process of the presentinvention are useful in a wide variety of applications in the field ofgraphic arts, due to their superior adhesion to metal surfaces,excellent resistance to most solvents and chemicals, and capability offorming high resolution images. Among such uses are photoresists forchemical milling, gravure images, offset plates, stencil-making,microimages for printed circuitry, thermoset vesicular images,microimages for information storage, decoration of paper, glass, andpackages, and light-curable coatings.

The procedures for mixing the radiation-sensitive compositions of thepresent invention are relatively simple. The polymerizable mixture iscombined with the organohalogen and organometallic compounds with asuitable inert volatile solvent. By such a suitable inert solvent ismeant any solvent which does not react appreciably in the dark with theepoxide material and catalyst precursor. Examples of such solventsinclude acetone, acetonitrile, toluene, xylene, methyl ethyl ketone,ethylene glycol, monomethyl ether, ethyl ether, dimethyl ether ofdiethylene glycol, monochlorobenzene, tetrachloroethane,trichloroethylene, 1,1,2,2-tetrachloroethane, o-chlorotoluene,o-dichlorotoluene or mixtures thereof. It will be apparent from areading of the solvents listed that many of the organohalogens suitableas catalyst precursors are also solvents for the compositions. Thus,these halogen-containing solvents may not be strictly considered asinert since traces left in the dried coating would act as additionalhalide photoinitiators. However, until exposed to light, e.g. in thedark, such compounds are inert and suitable for use as solvents.

The amounts of organohalogen compounds employed should be sufficient toinsure complete polymerization. It has been found that quitesatisfactory results are obtained by providing an organohalogen compoundin amounts by weight of from about 5% to about 50% relative to theweight of the polymerizable epoxide material, about 2% or less beingamply effective with some monomer-catalyst systems.

The organometallic compounds are employed in amounts relative to theamount of organohalogen employed. In general, such amounts may vary from1 to 3 cmoles organometallic compound per mole of organohalogen.

It may be desirable to include in the composition an inert pigment orfiller, which may be present in even a major proportion by weight.Inclusion of such inert materials usually makes advisable aproportionate increase in the optimum amount of organohalogen andorganometallic compound needed. Nevertheless, the amount of thesecompounds rarely exceeds 50% of the entire weight of the composition.

The following examples will serve to further illustrate the presentinvention.

EXAMPLE I

Two solutions designated "A" and "B" were formulated to contain thefollowing components:

    ______________________________________                                        Part A                                                                        Bisphenol A glycidyl                                                          ether polymer (Epon 1009)                                                                           21.7g                                                   Methyl ethyl ketone   16.2g                                                   Toluene               16.2g                                                   Part B                                                                        Methyl ethyl ketone   32.8g                                                   Iodoform               9.8g                                                   Triphenylbismuthine    3.3g                                                   ______________________________________                                    

The two parts were then mixed together and applied as a coating with aNo. 12 Mayer rod onto a silicate coated aluminum offset plate. Theresultant coating was allowed to dry in air in the dark after which itwas exposed through a Kodak No. 2 step tablet (this type of tablet has21 continuous tone steps varying from optical densities of 0.05 to 3.05)at 18 cm. distance from a Gates Raymaster 360 Watt Uviarc mercury lampfor 5 minutes and then heated at 110°C for 3 minutes. When developed inmethyl ethyl ketone by immersing the exposed plate therein and rubbingwith cheesecloth, a length of cured epoxy coating remained on the stripas a negative image, corresponding to the first six steps of the steptablet.

The same experiment employing Redicote aluminum offset plate as the basesubstrate reproduced seven steps.

EXAMPLE II

The following formulations were prepared:

A. 10.g. 50% ECN 1299 (an epoxy cresol novolak resin) in o-chlorotoluene

1.0g. iodoform

6 ml. acetonitrile

B. 10g. 50% ECN 1299 in o-chlorotoluene

1.0g. iodoform

6 ml. acetonitrile

0.336g. triphenylbismuthine

C. 10.g. 50% ECN 1299 in o-chlorotoluene

6 ml. acetonitrile

1.0g. triphenylbismuthine

D. 10.0g. 50% ECN 1299 in o-chlorotoluene

6 ml. acetonitrile

1.34g. bismuthtriiodide

The above formulations were coated onto aluminum plate following theprocedure of Example I and dried overnight in the dark.

Two types of tests were conducted: one to determine if crosslinking tookplace under various conditions and the other to determine to what extentcrosslinking took place. Specifically, the samples were

1. heated for 5 minutes at 110°C and developed in trichloroethylene or

2. exposed for 5 minutes to a Gates Raymaster Uviarc 360 W mercury lampthrough a mask or screen to leave portions unexposed and developed intrichloroethylene or

3. exposed as in (2) above for 5 minutes, heated for 3 minutes at 110°Cand developed in trichloroethylene or

4. exposed for 5 minutes under a Kodak No. 2 continuous tone 21 steptablet in contact frame and developed in trichloroethylene or

5. exposed as in (4) above, heated for 3 minutes at 110°C and developedin trichloroethylene.

All exposures were done at 19cm. distance from the light source.

The results are summarized in Table I.

                                      TABLE I                                     __________________________________________________________________________           Results of Treatments After Development                                                                           5 min. hv-                         Formulation,                                                                         Δ 110°C,                                                                           5 min. hv                                                                              5 min. hv,                                                                             Step Tablet,                       Additive                                                                             5 min.   5 min. hv                                                                              3 min. Δ 110°C                                                            Step Tablet                                                                            3 min. Δ,                    __________________________________________________________________________                                               110°C                              All of Coating                                                                         Hard Coating                                                                           Hard Coating                                         CHI.sub.3                                                                            Washed Off,                                                                            in exposed area                                                                        in exposed area                                                                        1 Step   2 Steps                                   No Cure                                                                CHI.sub.3 and                                                                 Bi (φ).sub.3                                                                     "        "        "        3 Steps  5 Steps                                            All of Coating                                                                         All of Coating                                                                         All of Coating                                                                         All of Coating                     Bi (φ).sub.3                                                                     "        Washed Off,                                                                            Washed Off,                                                                            Washed Off,                                                                            Washed Off,                                        No Cure  No Cure  No Cure  No Cure                            BiI.sub. 3                                                                           "        "        "        "        "                                  __________________________________________________________________________

It will be apparent from the results of the experiments reported in theTable that the combination of iodoform and triphenylbismuthine functionssynergistically in forming a cured photopolymer. It will also beapparent that triphenylbismuthine and bismuth triiodide are notinitiators of such crosslinking either thermally or photolytically.

EXAMPLE III Part A

The following formulation was prepared:

    ______________________________________                                        50% ECN 1299 in o-chloro-                                                     toluene              10.8g.                                                   iodoform             2.44g.                                                   methyl ethyl ketone  6.8g.                                                    toluene              4.0g.                                                    ______________________________________                                    

Samples of uncoated Redicote aluminum offset plate were coated with thisformulation and allowed to dry in the dark.

A sample was exposed through a No. 2 Kodak step tablet to a 360W mercuryarc for 5 minutes, heated at 110°C for 5 minutes and developed inacetone. Three glossy steps, followed by four dull very thin steps werereproduced.

Another sample was exposed for 21/2 minutes through a half-tone and lineimage transparency, and then heated for 5 minutes at 110° before finaldevelopment in acetone. A negative photopolymer reproduction of thetransparency image remained on the plate.

Part B

The experiments were repeated except that 0.885g of triphenylbismuthinewere added to the above formulation.

After exposure, heating and development as in Part A above, six glossysteps were reproduced.

The sample exposed 21/2 minutes through a half-tone and heated as inPart A above also yielded a negative photopolymer reproduction of theimage which was of better resolution and clarity than obtained in PartA.

EXAMPLE IV Formulation A

    ______________________________________                                        59.5% Araldite 7097 in                                                        methyl ethyl ketone  3.65g.                                                   methyl ethyl ketone  3.42g.                                                   toluene              1.6g.                                                    iodoform             0.98.                                                    ______________________________________                                    

Formulation B

Same as formulation A except that 0.33g of triphenylbismuthine was alsopresent.

The above formulations were applied to an aluminum plate exposed as inExample I and developed in methyl ethyl ketone.

A sample strip with formulation A reproduced 4 steps of the step tabletwhile the strip with formulation B reproduced 5 steps which were boththicker and sharper in definition than that obtained with formulation A.

EXAMPLE V

Two formulations were prepared to contain:

A. 3.62g allylglycidyl ether-glycidyl methacrylate copolymer

2.7g toluene

8.2g methyl ethyl ketone

11.63g iodoform

B. Same as formulation A to which 0.55g triphenyl bismuthine is added.

Separate coatings were made on redi-cote aluminum using a No. 12 Mayerrod.

Sample strips were exposed through a No. 2 step tablet for 30 secondsand then developed in methyl ethyl ketone. The coating with iodoformalone reproduced 15 steps while the coating with triphenyl bismuthinealso present reproduced 17 steps. Both coatings could be dyed with atrichloroethylene solution of Orasol black.

When similarly exposed to a Xenon lamp for 15 seconds and developed, thetwo coatings yielded 5 and 8 steps respectively.

EXAMPLE VI

A coating was cast on an aluminum plate from a mixture consisting of10.8g Epon 1009 in methyl ethyl ketone, 2.7g toluene, 1.0g carbontetrabromide and 0.336g triphenyl bismuthine and C.P. No. 4, atriphenylmethane leuco dye. After drying, part of the coated surface wasexposed to actinic light for 5 minutes. The light source was a 360WGates Raymaster Uviarc mercury lamp. Following exposure, the entiresample was heated for 10 minutes at 150°C. The unexposed portion of thecoating, before development with acetone, was found to be water whitewhile the exposed areas were blue. Upon development with acetone onlythe unexposed area washed off.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the matter of theingredients, the identity and their proportions and in the steps of theprocess and their order of accomplishment without departing from thespirit and scope of the invention or sacrificing all of its materialadvantages, the form hereinbefore described being merely a preferredembodiment thereof.

What is claimed is:
 1. A process for polymerizing a monomeric orprepolymeric epoxide material or mixtures thereof, whichcomprises:forming a mixture of a monomeric or prepolymeric epoxidematerial, or mixture thereof, polymerizable to higher molecular weightsthrough the action of a cationic catalyst, with a radiation-sensitivecatalyst precursor which decomposes upon exposure to electromagnetic orelectron-beam radiation to provide an active catalyst effective toinitiate polymerization of said epoxide material, said precursor beingan organohalogen compound wherein the organo radicals are alkyl, aryl,alkaryl, aralkyl, alkoxy and aroxy in combination with an organometalliccompound having the formula R₃ M wherein M is P, As, Sb or Bi and R is ahydrocarbyl radical or hydrogen with the proviso that at least one R isa hydrocarbyl radical; and subsequently exposing the resulting mixtureto electromagnetic or electron beam radiation to release an activecatalyst in sufficient amounts to effect substantial polymerization ofthe epoxide material.
 2. The process of claim 1 in which theorganometallic compound is triphenyl bismuthine.
 3. The process of claim2 in which the organohalogen is iodoform.
 4. The process of claim 1, inwhich mixing of the epoxide, catalyst precursor and organometalliccompound is effected by use of a solvent.
 5. The process of claim 1, inwhich the mixture is exposed to electromagnetic radiation.
 6. Theprocess of claim 1, in which the mixture is exposed to electromagneticradiation after which it is heated to an elevated temperature.
 7. Aprocess for polymerization of a monomeric or prepolymeric epoxidematerial which comprises:forming a mixture of a monomeric orprepolymeric epoxide material or mixture thereof, that is polymerizableto higher molecular weights through the action of a cationic catalyst,with a radiation-sensitive catalyst precursor which decomposes uponexposure to electromagnetic or electron-beam radiation to provide anactive catalyst effective to initiate polymerization of said epoxidematerial, said precursor being an organohalogen compound wherein theorgano radicals are alkyl, aryl, alkaryl, aralkyl, alkoxy and aroxy incombination with an organometallic compound having the formula R₃ Mwherein M is P, As, Sb or Bi and R is a hydrocarbyl radical or hydrogenwith the proviso that at least one R is a hydrocarbyl radical; Applyingsaid mixture to a surface area; Screening predetermined portions of saidsurface area; exposing the unscreened surface area to electromagnetic orelectron beam radiation to effect polymerization; removing saidscreening means; and thereafter applying a suitable solvent for removalof unpolymerized portions of said mixture.
 8. The process of claim 7wherein the organometallic compound is triphenylbismuthine.
 9. Theprocess of claim 8 wherein the catalyst precursor is iodoform.
 10. Theprocess of claim 7 wherein the energy applied is electromagneticradiation.
 11. The process of claim 7 wherein the energy applied iselectromagnetic radiation and heat.